The present invention relates generally to the process control and measurement field. More specifically, the present invention relates to a device and method for communicating with smart field devices used in process control and measurement systems.
Field devices are well-known tools used in the process control and measurement field. Field devices provide a user or control system with data regarding a particular process variable, such as pressure, flow or temperature. These devices are commonly employed in the petroleum, pharmaceutical, and chemical processing fields.
The use of “smart” field devices in process control and measurement systems allows for two-way communication between the field device and a communicator device (e.g., hand-held device or computer). Two-way communication is implemented using one of a plurality of communication protocols. However, a number of different protocols exist for smart field devices, each protocol requiring the communicator device to be configured in a different way. For instance, the highway addressable remote transducer (HART®) protocol allows a digital signal to be superimposed on the standard 4-20 milliamp (mA) analog signal. The HART® protocol employs a frequency shift keying (FSK) principle in which digital signals are represented by modulating the 4-20 mA signal±0.5 mA at either 1200 Hz (representing digital logic level “1”) or 2200 Hz (representing digital logic level “0”). The superimposed digital signal allows the smart field device to both send and receive digital data, and is commonly used to transmit upon request diagnostic and multivariable information to a control room or handheld device. Other popular two-way digital communication protocols include the Fieldbus™ protocol and Profibus protocol.
Because each communication protocol operates differently, the communicator device must be configured based on the communication protocol employed by the field device. To prevent the situation in which users must carry around separate hardware for each known communication protocol, tools have been developed such as the handheld 375 Field Communicator from Emerson Process Management that supports communication with both HART® and Fieldbus™ devices. The 375 Field Communicator provides an intrinsically safe device for use in any process environment. However, not all applications require the robustness of the 375 Field Communicator. For instance, bench-top commissioning of a field device (i.e., prior to installation in the field) does not typically require an intrinsically safe communicator device. In these situations, customers often convert laptops or other computer devices to function as a communicator. While economically attractive, this method of communicating with a field device requires a customer to acquire and correctly connect a number of different elements, including a communication modem or interface, a power supply and a measurement resistor. Furthermore, the customer must also acquire and install application software onto the portable device specific to the communication protocol of the smart field device.
It would therefore be beneficial to provide a system that would simplify the process of connecting a computer or other portable device to a smart field device for the purposes of bi-directional communication.